1. Field of the Invention
The present disclosure relates generally to packet network devices, and more particularly to intelligent control of traffic to IP (Internet Protocol) telephones.
2. Description of Related Art
Traditional analog phones transmit and receive voice-band analog signals on a dedicated telephone circuit. In contrast, an IP phone connects to a packet data network (Internet Protocol is a common packet format for “IP” phones, but the use of such phones is not limited to IP packet networks). Voice data is digitized, compressed, and transmitted by an IP phone in voice data packets according to one of several available protocols. Received voice data packets are buffered, decompressed, reconstructed, and converted back to analog form for playout to the user as if the user were talking on a traditional analog phone.
IP phones typically connect to a local area network (LAN). When a user dials a traditional telephone number on the IP phone, the IP phone contacts a known call management server (commonly called a “gatekeeper”), which may reside on the LAN, or on a Metropolitan Area Network or Wide Area Network reachable through the LAN. The call management server sets up the call with reference to its own policies and by exchanges, if necessary, with another server that manages the called station or an access point to that station. The call management server then instructs the IP phone how to contact the desired endpoint, either through the LAN, through a WAN, or through an access server that terminates the VoIP packet aspect of the call at a gateway to a traditional telephone network, which carries the call the rest of the way to its destination.
FIG. 1 shows some components of a LAN 100 that supports IP phone service. A switch S1 connects through one or more switch ports to a network 110 (a single network link NL1 is shown, although typically others will exist as well). Three other illustrated switch ports connect S1 to three IP phones (IPP1, IPP2, and IPP3) through three packet data links (L1, L2, and L3), respectively. A fourth illustrated link L4 connects S1 to an endpoint C1, shown as a computer (a computer may also contain a “soft” IP phone, e.g., software to place and receive calls over the packet network through the computer's network interface).
LAN 100 may be, for instance, an enterprise packet data network, with other switches and routers (not shown) to connect the illustrated systems to other sections of the LAN, enterprise servers, and the “outside” world. A gatekeeper GK1 also connects to network 110 through a network link NL2. IP phones IPP1, IPP2, and IPP3 communicate with gatekeeper GK1 to set up calls, either to each other, other LAN phones, or outside phones. Although call setup messaging is coordinated through GK1, once a call is set up (e.g., between IPP1 and IPP2), the voice data protocol negotiation and data packets pass directly between IPP1 and IPP2 via switch S1.
One common feature of desktop-type IP phones is the presence of two packet data ports. This allows the IP phone to connect to the LAN, as well as another network appliance, such as a computer, and thus allows both devices to access the LAN through a single network jack and cable. The IP phone allows the other network appliance to connect to the LAN through the IP phone. Bridge logic in the IP phone transfers packet traffic between the two packet data ports, while extracting/inserting call setup packets, voice data packets, and other IP phone-feature packets on the port connected to the LAN. Because IP phone traffic only uses a fraction of the bandwidth available on a typical LAN connection, a computer or other network appliance can utilize the extra bandwidth, allowing both the IP phone and network appliance to communicate simultaneously with the LAN over the single LAN connection. For instance, in FIG. 1 an endpoint C2 connects to IPP2 through a link L5, and an endpoint C3 connects to IPP3 through a link L6. Thus C2 and IPP2 effectively share link L2 to switch S1, and C3 and IPP3 effectively share link L3 to switch S1.